Iccarusamperex bugle boy best $ to performance. Find a good noiseless one.
Also if you have 6922/6dj8 tubes lying around you could use a 12AU7 to 6922 adapter. 6922's I believe run higher voltage so it won't be damaged running them lower from a 12AU7 socket, not sure how well they'd perform but I remember people having done it and working fine. Most tube amps these days are SS hybrids anyways.
That said 12AU7 tubes are generally cheaper so I'd start with those, if you buy ebay make sure the seller offers returns and RETURN it if the damn thing is noisy or hisses. Usually when you buy them for cheaper (under 40 bucks) you're going to find tubes that work bad for desktop amps, you just will. Incline they accept your full return if they sell you garbage, save your review as leverage.
rslataraThe rca clear tops sound quite good and I have some Raytheon (Baldwin) black plates coming as well, have a fair variety I’m rolling through already.