I happened to get a 15 by 30 heavy canvas tarp from the prev owner for $30. I was reluctant to drape it over the cabin roof and lifelines, as other posts here had warned that snow weight can crush the stanchions, and also if your mast is down (as I assume), people have had snow bend the mast if it is supported only at the ends.
I ended up building a frame from 1 1/2 inch PVC pipe from Home Depot, with 7 "A-frames" supporting a ridge pole. Each frame has vertical legs that go up from the toe rail to about the height of the lifeline, then a 45 degree fitting, and a length of pipe at 45 deg up to the ridge pole. To enable disassembly the tops of the 45 deg "roof rafters" are attached to blocks of wood with screws. Fixing the bottoms of the vertical legs was a tough challenge, as my 23 lacks a metal toerail with holes. I ended up glueing T fittings to the bottoms, and cut out an approx 1 inch slot in what would be the top of the T (which is against the toerail since these are inverted). That slot straddles the fiberglass toerail, and each is tied down to the trailer frame. The whole tarp (which was tough to drag up over the frame, since I did it alone) is then tied tightly down at each grommet to the frame or else under the boat to the other side. I can get in at the stern.
Low cost? The tarp was a bargain, as it is very heavy and much stronger than plastic tarps. The pipes, wood and glue (and misc) prob cost me around 100 to 120 - cheaper than one shrink wrap. It did take a lot of work, measuring and cutting to get the right orientation of the frames.
One warning - the scupper drain at the rear of the cockpit tends to accumulate debris and leaves if near any trees. The leaves flatten and effectively block the drain. The cockpit then fills, and if enough will flood the lazarrette and maybe interior. I believe this happened before I bought mine, and I think the cockpit water incurred through the round access port in the area where you put your gas tank under the seat. Easy for you to monitor since it sits at your house.