$tep ring$ are your freind$
O.k. so we are all on the same page, 77mm CPL on the 70-200 WITH the petal hood, then 77mm CPL with step down rings and RUBBER hood on Smaller lenses. right?
I haven't thought of a hood, although I remember don recommending one. Too expensive for a hood, damn.... I'll deal with a flare if it comes, but I will be careful.
But a 77mm multi-coated (HOYA) CPL with a 49mm to 77mm step ring set would be good.
49mm for your 50mm F/1.7 (although will probably vignette a bit due to the "hood" of the rings :D.
Got a 49mm CPL on my 50MM and a uv filter so I am good there, Need to go check and see what MM optic the Tamron 200-500 has.
general rubber lens hood (<- click here) is only around $10. Knock off a lunch or two, you can afford it.
Also, read through this older post concerning filters and step-rings (<- click here), from last August, I think. I believe you will find it familiar and right on topic (especially the last page).
You want to have some fun ... try fielding the cost of a 300mm f/2.8 lens. Now, that's a real bargain. NOT!
this will go for?
And 112mm filter.... whoo, don't even want to think about it.