There are 2 types of links you can use:
1. Direct link to the order page:
https: //www.plimus.com/jsp/buynow.jsp?contractId=XXX&referrer=YYYY

2. Link to the product website (as entered by the vendor in "Product URL":
http: //www.plimus.com/jsp/redirect.jsp?contractId=XXXX&referrer=YYYY
* Where XXXX is the contract id and YYYY is your Plimus username.