If you want good and cheap, the Elan IIe can be had for $25. Even better would be the Elan 7, currently going for about $60. Better yet would be the Elan 7N, for about $100. The Elans are light and extremely quiet.

The Rebel series are cursed with pentamirrors, except for the first two or three models. You can check the Canon Camera Museum for specifics. Pentamirrors are smaller and darker than pentaprisms.

There is a viewfinder extension that fits the K2 that you might want to have a look at. I had one once, though I wasn't entirely satisfied with it and haven't used it more than a few times.