Target Protein recommendation

Hello everyone,

I am planning a project to study protein expression analysis by
cysteine labeling, and I need to find a suitable protein as a testing
target. My equirements for the protein include:

Easy and cheap to obtain pure commercial sources (at least 95%, from
Sigma, etc.);
MW around 30 to 70K, only one subunit;
Average cysteine content, around 8 to 10;
Normal SDS-PAGE mobility to check modification.
Easy to purify from cell lysate, if needed.

Any recommendations? Thanks a lot for your help!


Tris
(PS. No albumin, please.)