Google eCommerce tracking fix for when a payment is completed transfering to a different secure domain

Google eCommerce tracking fix for when a payment is completed transfering to a different secure domain

Hi guys I have a problem with my google ecommerce tracking on my site. The problem is that when a payment is completed my site URL changes from:

www.website.com to website.securetill.com

The problem with that is when I look in my Google Analytics it displays the traffic source for all customer purchases to be from www.website.com because obviously the customer is converting on website.securetill.com and the last site domain they were on is www.website.com

The developers of our ecommerce system say they are unable to help us change this at the moment as they only have one area for providing a secure connection to all their customers. I'm told there may be a fix that can be applied using javascript but I've absolutely no idea how to go about something like this.

Has anyone else got this problem with their site and have they managed to create a work around?

Or does anyone have any ideas for making this work?

Thanks people