Do you just need a purchase order or do you also need a contract?
As a preliminary matter, remember that it is not necessary to create a contract every time you make a purchase — particularly a purchase of goods. In fact, most purchases made by University personnel are made by processing a purchase order with no other written agreement. (While purchase orders and acceptances also create binding agreements — we are not discussing those here.)
If a vendor is willing to sell the University a product without a contract, ask yourself whether there is some type of risk to the University that a contract might help mitigate? Usually there is no such risk and the purchase order is sufficient.
Furthermore, if a vendor wants you to sign a contract, it will probably be a contract full of terms that are favorable to the vendor and not to the University. Vendors and their attorneys are looking out for the vendors’ interests — not the University’s.