Prepainted plastic D&D Minis and Pathfinder Battles Miniatures are sold all over the internet. Miniatures Market is a seller with LOTS of options.
Can you rebase a figure? That at least opens up Heroclix, Horrorclix & Mageknight figures, which are also prepainted.
Post some stuff you painted. It's still probably better than the sweatshop workers who paint for the big companies.
Painting tip #1 Scrub the mini with dish soap, then rinse thoroughly. This takes off most greases, oils and mold releases that might still be on the fig.
Painting tip #2 If you are painting minis you prime (Most minis other than Reaper's Bones) , spray prime black with cheap spraypaint primer. Automotive or even walmart brand should work. Then drybrush the whole mini white. This creates a shading effect with most colours you will paint on afterwards.
IMO collecting minis can get expensive. What I have done with my group is use the paper pawns from Pathfinder. They are much lower cost and do the trick.
We had some players get a bit confused about who was who in a bigger fight, so I am thinking I will pick up the Icons of the Realms starter set to use as PCs. There are 6 plastic & prepainted minis in the pack, with two of them being female. That should cover "most" tables. IMO It doesn't matter if they look exacly like your character, just have everyone pick one they like and roll with it. That way they have a way to quickly tell who is who from a quick glance at the table.
Alternately, if money isn't an issue there are a lot of official D&D minis (plastic & prepainted as well) available.
Reaper mini also has a line of prepainted plastics, but note that the price point is higher than other prepaints because they are non random so they don't have HIGH cost rares making commons more plentiful (cheaper).
'Sadly' the success of their unpainted BONES line means the Legendary Encounters line doesn't get restocked as fast as it could be. (Same manufacturing assets i think)
For the PC's I just found out about this site a couple days ago and it looks amazing but haven't ordered anything yet. Heroforge https://www.heroforge.com/ it lets you customise to a point a minature.
Seconded on those Pathfinder pawns. My groups DM has the NPC and Monster Codex boxes, and they're great. Nice artwork, lots of variety, a lot less 'bulky' than miniatures.
I was pretty set on starting a collection of cheap, pre-painted mini's for a long time until I started playing with these. Now, I'm just going to pick up both boxes, put 'em on the bookshelf and be done with all of it.
If you absolutely don't want to paint, go with the paper mini's. You will get a lot more for your money than buying horrible looking pre-painted plastic mini's...
If you would like some fairly cheap 3D mini's, I suggest Reaper. That's where I get all of mine from. To save yourself some money, because minis can get expensive, I recommend buying mini's from Reapers Bones line. They're just a nice, but made from durable plastic rather than metal.
For the PC's I just found out about this site a couple days ago and it looks amazing but haven't ordered anything yet. Heroforge https://www.heroforge.com/ it lets you customise to a point a minature.