If you just want like a 1 time feedback slapback delay, I guess the question is do you want it to sound super clean or kind of old and vintage. Also how much $$ do you want to spend.
A lot of people have something against Boss, but I think the DD-7 is a great delay and you can definitely get a super clean digital slapback delay with that no problem, it has various different timing settings for super quick delays or super long delays, and a feedback knob that you could easily set to limit the feedback to one. Any digital delay pedal that is more expensive will also easily do that - for example the Eventide Timefactor which is pretty much one of the best delays out there.
If you want it to be older or vintage sounding, I use a Mooer Ana Echo for that, its supposed to be a clone of the Boss DM-2, a super classic and pretty prized delay according to some. You could easily get a slapback with that too probably, but that's not what I use it for. I'm sure any other vintage delay will do that too, but real vintage delays could get a lot more pricey.
I'd go with the Boss DD-7. And the ridicule ensues...