In the next few weeks I will be putting a (temporary) L-Jetronic 1.8 engine in my 914.
I am not sure I have a working bosch pump, so what is the preferred aftermarket pump these days?

Figure with all the EFI cars they should be easy to find, and guessing I will need a regulator to bring the pressure down to the right spec.

Get an Airtex E8445 or equivalent. No regulator, other than the factory one is needed.

Available at your FLAPS.

Been running one on Betty's car for years. Works perfectly. Rob-O is running one on his L-Jet car.

Yup, what Clay said. Works well. The inlet size to the pump is a little large if you're using the factory fuel lines sizes. But it's really easy to rectify the issue. The inlet comes as a brass fitting that screws onto the pump. You cut the barb off that brass fitting, then tap the hole left behind. You then thread a small Ford fuel filter into the tapped hole. It's a brilliant solution, really. The pump is an Airtex E8445 as Clay said. Tap was 1/8-27 NPT. I don't recall the fuel filter (but I bet Clay knows it off the top of his head). I used some self-tapping screws from the local hardware store and mounted the pump on the firewall.

I got all of the parts (pump/filter/tap) at the local O'Reilly's for ~$100. All of it was in stock (pump, filter) or hanging in the tool section (tap).