Yeah, you sure can get them chipped up. You can do it the stupid way, the nasty way or the easy and expensive way.
The stupid way is to get a "neo key" this requires you to solder 1 wire inside the PS2. Quite a few PS2 backups can detect a Neo key and stop the games booting so its a pointless escapade. You also need an action replay cartridge for this to work which is another £30.
The nasty way is goto a regional computer fair in the UK and buy a £3.50 "NEO2" or "NEO3" chip and fit it yourself. Its a icky job, requires a special cool very small 15W soldering iron, a steady hand and 8 bits of wire. The downside of this is you will need to have an action replay 2 card to boot your "backups", also some EA games won`t work on this chip. Also this chip can stress your PS2`s laser which means more wire modifications later. Sometimes the chaps at the fairs will fit em for you for anything upto £50.
The other method is find someone who has got a shed load of chips called "messiah-lite" (sony jumped on Messiah`s production crew before they could get it finalised but some of the last beta chips are still on the market). The messiah has over 20 wires, and involves the soldering skill of a genius but will play any ps2 backup including booting up and dvd games. The people who sell these are usually fitting them aswell. I`ve known people pay anything upto £100 for getting one of these sods fitted. The short supply means the chips change hands for anything upto £50-60. There is talk of a messiah 4.5 on the market but i`ve not come across any yet.
Personally, I`ll wait until someone comes out with a simple plug in card that allows you to do it with no hassle and less cost.