What do you mean by "through hole termination" ? Pogo pins by their nature they are "through hole", put them through a hole and solder. Do you mean some sort of flange to locate it?
Anyway, obtain some pogos which will be able to meet your pitch requirements, and make an extra thick PCB with the appropriate arrangement of holes, or stack several together to get the thickness - reason for thickness is to make your alignment job easier - insert the pins, and solder in place.
Remember, if you're making your own programming attachment, you can make your own footprint, nothing to say your holes all have to be in a line, you could make them staggered, or circularly arranged to save space.
PS: if it's for one-offs, don't overlook the fact that you can just plonk pads for the SPI pins individually anywhere and solder flying wires to them temporarily for programming then remove them when you're done, do that quite often, saves having to route traces to a programming header.
PS2: you can also mount the pogos flat on either side of an appropriately thin PCB, say probably 0.8 to 1mm thick. Use two connected long pads for each pin so the pin is cradled in the middle of the two for alignment, solder them in place.