Raymond_B wrote:

I can help with 3D printing if that's what you need. I also have Solidworks and can help design, maybe I am no SW pro, but would be willing to help.

 
I'll try to sketch something up.  Thanks

What part is bent at the 25 deg angle? Is that the sides or back of the top plate?

RTM wrote:

Raymond_B wrote:

I can help with 3D printing if that's what you need. I also have Solidworks and can help design, maybe I am no SW pro, but would be willing to help.

 
Looking at two different ideas. Both are two piece, one will just be two flat pieces and the other idea is to make the top piece over lay the bottom piece covering the entire outside edge. This idea will allow me to just put the boot between the two pieces and have a cleaner look.

Raymond_B wrote:

Is this what you are thinking?

 
How much to have you make me one?  😁

Bob, if I am getting this correctly, the big part will hold the smaller part down once the boot material is wrapped around the smaller part.  That would be a very clean setup.  Couple of suggestions if that's what you are planning:  Add a couple of screws in the center of the long sides to prevent bending.  Unless your boot is made of very flimsy material there will be significant load involved in holding it together...thinking expanded vinyl or thin leather and the wrinkles that may be unavoidable.  Next, be sure to dimension the parts so the recess is loose enough and deep enough to accommodate thickness of the fabric and allow the outer part to completely cover (hide) the ring with the fabric wrapped around it. 
I believe 3D printed would probably be stiff enough to work with a lighter vinyl material, though, you may want to add two screws to each side to make sure it pulls down evenly.  At 1/4" thick, machined from aluminum would work well but I would still add a screw to each side. 

Also consider the overlap seam of your material in the gap as that will possibly deform or break when clamped down.