There are a couple of games out there for the Toppy - Snake, Chess, Poker etc (listed on toppy.org.uk)

Does anyone know of any others available? I'm particularly looking for arcade game clones such as Tetris, Space Invaders, Puzzle Bobble etc.

There's a Sudoku, plus a few built in ones. I think one of those is similar to Tetris; try www.tapworld.net for some others, but I don't think there are that many. I think someone did port Doom once; maybe if you've time on your hands you could tackle MAME

I found a couple games designed for the TF4000 here:

http://web.utanet.at/nkehrer/

Anyone know if these will work with the 5800???

The answer is no

Why not email the author and ask if they'd be able port it?