I have looked at Doc's website and have called to see if he has a template. No luck.
Make your own template - it's easy! Get a piece of plastic - I go to Lowes and buy a 4mil drop cloth for just a few bucks - and stretch it over the tub. Tape it in place, and get it as tight as you can. Then just draw around the top of the tub with a marking pen. Draw your line as big or as tight as yo want it. If you draw it a half-inch down from the top all the way around, your cover will be just slightly oversize, and that's usually just right. Of course, you can also measure your old cover and send the dimensions along with the template so Doc can fine tune it for you
I cut the excess plastic sheeting off, mark my name and the make and model of the tub on the template - mark "This side UP" if it matters, that is, if the cover is not concentric, or if you want no skirt along one side or whatever - pack it into a USPS flat rate box for $6 or whatever it costs, and you have it made in the shade.
Mark the locations of the fastners - keep in mind that you can add more or delete them as you wish since this is a custom cover - and ask Doc to give you a call when he has it in hand.
HTH