Amazon:
Rugby 06 - $17.99 - http://www.amazon.com/Rugby-06-Playstation-2/dp/B000CRSBL6/ref=sr_1_2?ie=UTF8&qid=1309430679&sr=8-2
Rugby 08 - $29.99 (Pre-owned) - http://www.amazon.com/Rugby-08-Playstation-2/dp/B000Q2PG6K/ref=sr_1_7?ie=UTF8&qid=1309430679&sr=8-7
You wont find them in any shops these days, your best bet is Amazon, but I dont know how expensive $29.99 is for an older game, im guessing around £17 which isnt too bad, 06 is relatively cheap.