This might not help at all have but you thought about the BL range from celestion.Ive retro fitted 10's into a Hartke tp 410 cab with very good results,the tone is a lot more vintage than its counterpart,my other TP with alli cones.I have two friends who've also fitted the BL range into their cabs with good results,a pair of tens went into an SWR redhead,it sounds great and Nick Carey,a well respected guy of this forum has fitted BL12's into his two 12" cabs,again with very good results.
They might be worth considering if you cant find the ones you're looking for.