Once you know which products fit your needs, there are several sources to contact to find those products. Below is a list of a few of the used equipment dealers. You may know of one in your area. Check the ads in magazines like Popular Electronics. Up to top 3.
Sampling techniques are the answer.
Sampling has been a viable method of reproducing high-bandwidth repetitive signals for many years. You could learn more about sampling techniques in the document called Sampling Techniques Primer , Tektronix literature number 47W-7209. Up to top 4. I have been using a 7633. Presently, I use a camera to capture the image and document my project.