Hi AK,
I bought mine from a chap in Bracknell, but there are plenty of sale on
ebay Prices start from £63 (beware of the very low prices) with free shipping.
I would suggest you chose a seller that ships from UK (reduced shipping time), has good feedback and accepts returns in case you have issues. I've noticed there are several Best Offer listings at the moment.
If you're interested I can show it working with my DiCE. I usually drive past Reading on Saturdays or you are welcome to pop down to Newbury any day of the week.
You are looking at a TCO of cca. £210. Reading on the forum here, prices for a one-off reading start at around £30 (dealer probably higher). I cannot comment on this as didn't need to bother since I have my own setup.
p.s. if anyone needs reading the codes from their Volvo in the Newbury area, happy to help, no cost.