Well there are two ways to do it, by the RAW, provided the DM (meaning the OP in this case) either: method 1) allows for player created items or, method 2) allows for munchkinly effects with spells.
Method 1) Get the Craft magic Arms and Armor feat, be of good alignment, know how to cast
fly then spend the time and requisite 12,550 gp + 1,004 XP. Those are the prereqs to craft the armor. Just because the description says "bright silver or gold", this could just as easily mean
color as the the actual metals
silver or
gold. Mithral is a "silvery, glistening metal" and matches that description. Of course, maybe all celestial armor is
already made from mithral, thus the "bright silver" description, and thus this point is moot. Or "bright silver or gold" is just a description and celestial armor's max dex, check penalty and ASF chance benefits are just part of the magic to enchant it. This makes "celestial" into a
package which could be added to any armor with a +22,100gp price modifier which would give that armor a +3 enhancement bonus,
fly (as the spell) 1x/day on command and grant a +6 max dex increase, lessen check penalties by 3, -10% to the arcane spell failure chance and halving the armor's weight. Then you could ignore the "bright silver or gold" as 'flavor text' and make "celestial" armor out of whatever the DM will allow. You could even say that adding "celestial" to the armor
turns it bright silver or gold (crafter's choice) so that all celestial armor
looks "celestial."
Method 2) Munchkinny nonsense plausibly allowable per RAW with a
very generous DM. Hit the celestial armor with
Dispel Magic until you succeed. Per the spell description- "If you succeed, all the item’s magical properties are suppressed for 1d4 rounds, after which the item recovers on its own. A suppressed item becomes nonmagical for the duration of the effect." Since it's temporarily non-magical, cast
Polymorph Any Object on it and change it from a "bright silver or gold" suit of chainmail to a mithral suit of chainmail. Since this change is within the same kingdom, class and size the change will be permanent. When the
Dispel Magic suppression wears off, provided the DM didn't just look at you funny and then smack you upside the head for attempting this, you should have a mithral suit of celestial armor. Or he could rule it changes back to normal, losing it's new mithral-ness, because "celestial armor" is magically made of an unnamed "bright silver or gold" metal that
isn't mithril and that quality was suppressed along with everything else. Or he could rule that the suit is now a magic item again and no longer affectable by
Polymorph Any Object, so the spell effect goes away. Of course, even if he does allow it, if it gets hit with
Dispel Magic, the change caused by
Polymorph Any Object can be dispelled changing it back to normal.
BTW, since I'm bringing up munchkinny nonsense, you can't have "Celestial Mithral Demon Rhino Hide Armor" either. One, because rhino hide armor is specifically described as "made from rhinoceros hide" (as opposed to celestial's "bright silver or gold" that could be either the color
or the metal) and thus cannot also be made from mithral- unless you can somehow find rhinoceros with a natural mithral hide. Maybe a rhino with the half-dragon template:Mithral Dragon. Two, 'celestial' and 'demon' have opposing auras- [good] and [evil]. One item can't be both.
So- using the 'package' idea from method 1 above,
IF you can find a half-mithral dragon rhinoceros, you could make mithral rhino hide armor that was either 'celestial'
or 'demon' AND you could give it Mighty (
Cleaving I assume- not sure what "mighty" by itself could be), Ghost touch spikes that were Anarchic
or Axiomatic AND Holy
or Unholy.
