Remember that if you want to source a used item that they are not compatable with 1.9D/TD/TDI, only pumps from 1.6D/TD and 1.7D can be used.
If you want a new one, the ones from Vaico, febi and Pierburg all appear to come from the same South American source, so pease do not pay a premium for a Pierburg item as the same thing can be bought for much less elsewhere.
We have had good results on T3 with the above brands, we however recently bought some "Brax" item from JP Group and the quality doesn't seem that great.