those things are generally mutually exclusive :bang: as those would be the holy grail...
How are you lighting it? Are you wanting to keep the texture of the background in, or are you wanting to low key so totally black'd out background?
The reason I ask, its it if fairly easy to light low key portraits with lighting from each side, making sure there is no light spill onto the back ground... in this situation, its the distance from the subject from the background which is also critical. You could with a grey/black background sheet making sure the distance and light spill is appropriate. You could do this for well under £100 with a 2M / 3M sheet and background frame holder...
If you want a higher quality background that needs to soak in alot of light as you'll be lighting subject from the front, then I think Lastolite do a few pop-up backgrounds of different material including a velvet-like material.