I'd look at a pick-n-pull first. Yeah you're likely going to get an older pump that lasts you a year or two, but right now thats what you need, isn't it? You can get one for $15-20 there and add in the gaskets, and even replace the fuel filter (and maybe the lines if they need it,) for under 50. Obviously get new filter, gasket, ect. new from fcpgroton....

I wouldn't get the knock-offs. They tend to be undersized or whatever and break faster than the OEM. While you're not planning on the car forever, it'd be nice if you didn't have to replace the pump next year (talking from experience here..).

Finally, are you sure the pump is to blame? The mechanic has determined this from the pump not high enough pressure, just not spinning, or what? Because eliminating the Fuel pump relay is easy (and free). The filter's clean enough that its not blocking flow? It'd suck if you replace and then find out thats not the problem. While most mechanics are very good, many don't work regularly on volvos and therefore don't know some of its tricks...