I'm rebuilding the shocks on a '65 Vespa, and the spec calls for Univis HVI 13. I found some other equivalents, but they are all either out of production, no longer contain seal swell additives, or are only available in 5 gal drums (I need less than a quart):

American Oil Rayco 746
Esso/Exxon Univis J 43 (different numbering system?)
Fina Hydr. Oil D 3011
Mobil Shell Aeroshell fluid 4 Aero HFA
Texaco 641
Shell Tellus 13
Shell Morlina 10
MobilFluid 62
Bel Ray Fork Oil w/Seal Swell 10 & 15 (mix to get 13W)

Any suggestions would be greatly appreciated. It's hard to find stuff that still has seal swell, and is in a size that's useful (and affordable).