Industrial DC/DC converters come in standard sizes and pinouts, so should be plenty of alternatives; pretty much anyone who makes them (Cincon, Recom, Murata, MeanWell, …) will have something that works here (this is pro stuff, though, so you won’t find it at Tayda and they’re not supercheap).
Look for dual supply +12/−12, 15W minimum, suitable Vin range (usually 9.0-18.0) and 2"x1" DIP footprint (but double-check pinout before ordering). E.g Recom RP15-1212DF, the Cincon EC5BU-12D12 linked earlier, MeanWell DKA15A-12, etc.
EDIT: The ones I mentioned are 9-18V in because that’s what you highlighted, but you say 18-36V in the comment. Adjust model numbers accordingly 
(RP15-2412DF, EC5BU-24D12, DKA15B-12, …)