Not sure if these links will help - they basically offer suggestions. If you're trying to keep it close to original you may have to cannibalize one from a broken siphon, or look at a lab supply house.
Just got one of these. How do people attach the siphon hose to a faucet? I tried bathroom and kitchen sinks, and the bathtub spout, and the spout to which the hose from my washing machine (in the basement garden-hose type fitting) ... to no avail. It won't fit snugly on anything, so...
www.photrio.com
My ancient Kodak Photo Siphon needs a part, a rubber adapter to connect it to a kitchen faucet. I can't find a suitable part anywhere. This used to be something carried in every hardware store,...
ask.metafilter.com
If you're not trying to keep it original looking, you can get creative. Depending on where you want to use it or what type of faucet you are connecting to, you may be able to come up with something better.
Many wash-tub faucets have threads that will take a garden-hose-style female end, The threaded fittings are fairly standard, and you can get something that reduces to the size of the rubber hose. You can even get a replacement aerator for a standard bathroom or kitchen faucet that will have male threads on the outside. They aren't pretty, but can be useful.
I have a washer for film reels that I put an adapter on - a plastic unit for a removable "hand-held" shower head. I used a hose clamp to attached the fitting to the hose. The fitting is similar to this:
Swivel adapter
You may even find a cheap handshower head with hose - just slice the hose off and connect it to your siphon.
First I used a replacement aerator on the bathroom faucet, but that was too much of a hassle with the small sink basin.
Instead, I purchased a diverter valve, and put that between the pipe and the shower head. It is similar to this:
Diverter
I can screw the hose onto the fitting, and then turn the valve so I can send the water to the film washer instead of the shower head.