Adapters off eBay from here: http://www.ebay.com/itm/221065459067?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648
Beware...the pins are a tad long, so don't push them in hard or bottom them out.
I tried to get adapters from Woo but the demand was too low for them to do a 1 off adapter with this pinout. If enough demand pops up and they do a run of these, I'd be in for a pair.
...Update on the sound: Simply outstanding! The mouse ear 6SN7GT sounds effortless driving the 421A. The soundstage is super deep and the mids and highs very detailed. The sub bass is not as pronounced as with the A frames, but the feeling of space feels somehow more realistic.
...trade is that you end up with less drive into the power tube, but I don't play anything that loud that I notice.
Edited by GrindingThud - 10/14/13 at 2:53pm