Where is the best place to buy a fuel pump for a 1974 1.8 liter? They don't seem to be that common.

List of 914 friendly vendors in no particular order include:
Pelican Parts
German Parts and Restoration
Automobile Atlanta
BusDepot
Cip1
Autohausaz (maybe azautohaus)
Performance Products/Automotion

I beg to differ...

that list of vendors appears to be in alphabetical order.

!!

Because the available pumps, if indeed they ARE available, are relatively expensive, you might want to consider using the 2 port pump common to the '75-'76 914, '75-'79 VW T1, and '75-'91 VW T2. Minor simplification of the plumbing is required, and you must use the later model fuel filter. This conversion means you have a NEW Bosch pump, not a cheap Chinese knockoff (with a horrifying record of reliability) or the unknown quantity of a rebuilt one, and at well under half the price (possibly as low as a third the price!).

The Cap'n

fixed that for ya

There is also a German made Peerburg pump that is a replacement for the stock pump. It only has two lines, so you have to take the T fitting out of the plumbing and put a straight piece of hose in, but otherwise it works great.

Because the wholesale price of the Pierburg pump is about $70 greater than that of the Bosch, it's unlikely you'll find one for a better price than the Bosch version. Besides that, the Bosch pump fits into the original bracket and uses the same pushon electrical connectors.

The Cap'n

I just bent over and purchased a Bosch from Pellican ~$140 ish. This replaces the original after 35 years. Thats pretty good bang for the buck it it goes another 35.

Rocky