My friend that I used to play with back home made a little booklet of tables that help you generate crazy magic items and put it on Amazon as The Book of Ten Trillion Things. You follow the rolling rules, roll randomly, and the adjectives build off each other until you've come up with some abominable concept. It's then your responsibility as a DM to explain exactly what the thing is that you rolled up. The book is completely system agnostic.
To give an example, i just rolled up "yielding mature woven slate mail." There are no mechanics involved, but now this gives me fuel to come up with an interesting item for my players. I decide that it's an ancient (mature) +1 set of half plate that gives no penalty to stealth checks (yielding, flexible) made with a woven structure (woven) that supports exceptionally durable pieces of slate, crafted by dwarves (slate).
"Sharp cloven luminous blood shortsword" - I rolled this one next. Let's see. This shortsword that bifurcated tip like the tongue of a snake (cloven). It's so sharp that attacks made with it crit on a 19-20 (sharp). When blood touches the blade, it sheds light like a torch until it's cleaned, sheathed, or until you take a rest (luminous blood).
"Light saffron maple map" - My buddy's book includes tables for everything from spoons to animals and carts, not just weapons and armor. I rolled this up and decided - This map is made of thin layer and almost weightless in your hand (light). It was crafted by wood elves from a thinly sliced cross section of maple, dyed a brilliant yellow color (saffron, maple).
"Rectified drab revolutionary yolk stinging cup" - Hmm. This is a wild combo of descriptors. This is mundane looking cup formed from dun-colored ceramic (cup, drab). It is used in an ancient rite of rebirth (rectified) involving drinking the poisonous yolk from a cockatrice egg (yolk, stinging) and it empowered the people of a forgotten civilization to overthrow their despotic medusa rulers (revolutionary). If you consume the contents of a cockatrice egg from this cup, you must make a DC 12 Constitution saving throw. If you fail, you are poisoned until the end of your next short rest. If you succeed on the saving throw, you are immune to petrification until the end of your next long rest. Once the cup has granted a creature immunity to petrification, it ceased to function until the following dawn.
All of this stuff I just roled randomly and came up with explanations off the cuff. His book is pretty expensive for it's size but I'm sure there's something similar you can find online to inspire you.