Both the pickups that SD recommends (Jazz and '59) look like PAF style pickups. SD doesn't give a lot of info other than resistance scores. Not sure what the "Jazz" is...but from the description maybe like a PAF with Alnico II magnets (sometimes called '57...I think that's what a Seth Lover is as well). Or a '59 with Alnico III magnets.

SD only publishes the resistance specs, but what would be a bit more directly comparable are the inductance scores. If you have a multimeter that will get inductance that might be useful in matching output. If you know the inductance from your JB you could ask Australian mfgs what they have in a pickup with just a bit less output.

I don't know much about Australian pickup makers. JJ's look like they'd have something that matches but they are pricey. Martin A Smith has some interesting pickups and publishes resistance and inductance specs, and they seem a lot more reasonably priced. There are a number of custom shops like "Mr. Fabulous" and Brierly that do custom winds at what look like OK prices. I stumbled on Australian pickup makers a few years ago and was impressed by what you could get for pretty good prices. I have no idea how good they are, but I have had good luck with a custom builder in Michigan and do like the personal touch ;-) Hopefully others may chime in with more helpful suggestions.