Looking at the Amal lists for the 276, seems there were two types of bottom feed, your sort with
nipple and gland nut on a threaded extension from the float bowl (the nut they say is unavailable but is 1/4 BSP on one I have here; the 1/4 inch nipple is available) or the sort with a
banjo, which comes in a twin-feed 'V-shaped' version for them as wants.
For the banjo the bottom fitment in the float chamber needs to be the sort with the plain section and cross-drilled hole for the fuel, not fully-threaded and drilled axially.
The brass fittings don't seem to be separate items, although both sorts of float chambers are available new at a price. (Dunno about the available angles of inclination though). A 'make' of the brass feed part would not be beyond the wit of man though, I feel pretty sure.
An alternative, if you could create a leak-free single feed at the base of the chamber would be a simple T piece in the fuel lines north of the carb - they exist and should be easily sourced if you can solve the leak.
I'd have said it was more common for leaks to occur on the connection at the bottom of the carb body than at the float input (as well as, commonly, some leakage from the float chamber lid).
Might be worth very lightly polishing with fine paste the seat for the nipple on yours to see if it can be persuaded to seal properly? Or re-soldering what looks like a perfectly OK bit of plumbing if the leakage is at the joints?
The pix here show the options as per Amal's current listings if you haven't already been there and come away disillusioned!
http://amalcarb.co.uk/generic-type-276.htmlJust to say - there were good reasons for the introduction of the Monobloc! My one machine with a Type 276 has a 376 Mono fitted, with the separate float jobbie safely in a box for the next owner if he or she can be a**sed with it.
