You can make your own lazy jacks from some small blocks and 1/8 inch cord but price
it out as the kits are not much more. The sail bag with a zipper is called a stack pack. You attach the sides to the boom and run a long zipper. Make a flap over the zipper to keep the rain out. You build the pack inside the lazy jacks.
The trick with the lazy jacks is setting the lines so as to minimize the tips of the battens fouling in the lines. Our firs boat they put the top line on a block so the jacks has a halyard
on each side. Then you could lower them when needed to raise the sails
. We don't have halyards now so you just practice raising the sail so you time the ends of the battens to miss the lazy jacks. It just takes a bit of practice.
If you hand flake the sail as it comes down you can train a little bit of memory to the sail making it fall quickly and neatly. We don't use a stack pack but just have a cover with 4 zippers on the side and a set of flaps with twist locks so the cover goes between the jacks (3 on each side of the boom. I like that better because the bottom is loose and lets air under the cover if the sail is wet. A well made sunbrella cover could set you back $450. That includes chafe protection and some other nice details. If you wanted to make your own the trick is to cut the slots for the lazy jacks last then add the zippers. No way can you measure right for the zippers. the last folks that made ours did it that way and they claim it works better since they don't have to remake them when things are not right.