If they won't refer you (usually because it's too much work but sometimes because of company rules) try getting a testimonial.
First ... write the testimonial you would like them to give you. Then ask them for a testimonial (written referral). If the response is "Write it up and I'll sign it", you can then hand them your prepared testimonial which they can copy onto their own letterhead.
Store the original away, then, use the bits you wanted (you did write it that way didn't you), in all your marketing contacts (letters, brochures etc.).
If you get a really good line (or better still several quotables) add it as a tag-line to your corporate signature. With modern word processing you can cycle through these testimonial sigs with every letter etc.
If they won't write a testimonial ask if you can use their name on a client list.
If a client is happy with you they will often let you do one out of the three.
One thing, be prepared for the answer they are not allowed to endorse suppliers with a solution (for example quoting without the company name). Better still, sit down, brainstorm all the possible objections, and document the objection and solution. Then after you've asked add any new objections and figure out a response.
Then get out and ask.
You won't get all but you will get some and that's a good start.
(who's hoping this made sense because he's so sick right now he can't be sure!)
Keep Up with TechRepublic