There are a number of PCI to PCMCIA adaptors available.
We've tested quite a few and selected the Elan Digital Systems P111 card (
http://www.elandigitalsystems.com/adapter/p111.php) for use with our 3G data cards.
These will be available shortly through the normal retail channel. RRP should be under R300.
Please be aware of cards that extend the PCMCIA connector with a cable to the front of the PC. 32bit cards (most new cards including the 3G cards) will not work or will be very erratic in such a setup due to the higher bandwidth requirements. These extended adaptors are only recommended for 16bit PCMCIA cards.
This implies plugging the 3G card into the back of a PC, so keep in mind you need to get to the back of your system.