Has to be a pre-'88 Mk1 Uno Turbo. Later Mk1 and Mk2 Uno Turbos have a different gearbox, which has internals of a design that won't fit in the X1/9 casing.
In San Francisco (is that where 'bay area' is?) that's going to be impossible. They were never sold new in the USA. Probably your best bet is eBay.co.uk and pay for shipping
Having re-read your post, I wonder if you were intending to buy just the turbocharger and bolt it onto the X1/9's engine... there's a lot more to an Uno Turbo than that... The bore and stroke is different. There are oil spray nozzles to cool the underside of the pistons. The cam is different and the compression ratio is lower. There is electronic ignition with crank angle sensor and electronic injection (Bosch LE2 Jetronic, similar to USA injected X1/9s but of course the ECU is programmed for positive manifold pressure up to 1 bar). There's even an oil cooler and intake air intercooler... you would need all those bits. You should, though, be able to bolt the X1/9's gearbox straight onto the Uno Turbo engine (not sure why the need to swap parts was suggested?)
Another option is to have a turbocharger installation developed locally, with a head gasket shim to reduce the compression, and aftermarket engine management to handle the fuel. Probably cheaper than getting an Uno Turbo engine, and although maybe not quite as reliable, it would be an interesting ride...
I myself would go for the 'hot 1500' option, as I've said in another thread

-Alex