Make one from cheap PVC parts. Either a largish one as described on the
NAR web site, or a smaller tripod using a "side outlet elbow". Available in 1/2" (model rocket sized), 3/4", or 1" sizes.
I built the larger version along with a pivot head made from eye bolts and a turnbuckle to hold the rod.
I was going to suggest something similar. I've made several pads like this lately with the side outlet elbow as the top of the tripod (3/4 and 1 inch sizes). I used PVC electrical conduit male and female threaded adapters to make the legs screw on/off (the electrical parts are cheaper than the similar ones in the plumbing department for some reason).
I also made eyebolt-based pivot heads, but with modified coupling nuts (drilled/tapped for a thumbscrew) to retain the rod. If you use 1/4 inch hardware this setup will take 1/8 or 3/16 rods and will nicely hold either an Estes blast deflector or better the heavy duty one from NARTS. If you choose your part lengths right you can also use a couple of legs of the tripod as a launch rod container.
The 4-legged cross-based on on the NAR site is rather more awkward to set up than a tripod in my experience. I've done those in the past up to and including one for a six foot 1/4 inch rod (for TARC).
Another tripod approach I've used is to use two different sizes of pipe (1 inch, 1 1/4 inch schedule 40) to make one leg's length adjustable. Then the rod holder can be fixed either as in the NAR page linked to above or with a fine-thread 5/16 bolt and a drill chuck harvested from a dead drill you have around the house or can get at a thrift store. My current 1/4 inch rod pad is set up this way. The eyebolt-based pivot could actually be combined with this if one chose one's hardware right.....
I've even tried to make a rail pad this way, using half inch hardware for the eyebolt pivot and 2 inch pipe for the tripod itself (got the side outlet elbow for this from Amazon). It's hard to get the pivot to hold the rail steady, though...need more friction between the two eyebolts. I currently have a rubber washer in there, but it makes the rail feel insecure even when it isn't, so I'm still looking for a good solution there.
