You could try
http://www.provantage.com - i know they ship internationally, as i have bought hardware from them before. So you shouldnt have any probs from them.
Also from what i can tell the X1550 is the better card, but its just an overclocked X1300 with the core shrunk to 80nm vs. 90nm.
Heres the cheapest X1550 at provantage in PCI:
http://www.provantage.com/data-x1550pro256psb~7BESD04M.htmbefore you order it
call them or email them and double-check it is a PCI not PCI-ENote this is TWICE as expensive as the PCI-E model, and the PCI-E model would run rings around it too.
Also note, that your power supply may not be up to running the X series radeon cards. Check your power supply wattage rating meets or exceeds the required amount for the card you're interested in. If not, you'll have to upgrade that too - more money.
So by the time you paid for a new card, new ram, new power supply, you've probably already spend $200+ odd USD - money which would be better spent on modern hardware which is cheaper, faster, and gives you more scope in the future.
You could always buy a 2nd hand machine for gaming only with a PCI-E slot. Then the sky is the limit with video cards. You can keep your business machine as is, and have a gaming machine which can grow as and when you need it to.
Oh, and what OS are you running? XP, 2000?