Here's a source for the UC caps you're after:
http://www.boiaudioworks.com/index.php?cPath=78&language=en
Just curious, which amp is this for?
My Mark IIB had a pair of 220uF / 275V caps, which I replaced with Illinois 220uF / 300V.
It's hard to fully re-cap an amp without buying from multiple suppliers. If I thought there would be enough demand, I might consider sourcing a bunch of capacitors and putting together re-capping kits for various amps so people could have a single source.