Here's the assembly manual. DIY might be challenging with little sailing experience, since you don't really understand the systems. Look on eBay, craigslist. Maybe you can find a 12 that's got a trashed hull to salvage parts from.
https://www.hobie.com/support/holder-12/Specs for the 12
https://sailboatdata.com/sailboat/holder-12Specs for Laser
https://sailboatdata.com/compare/result ... gn=compareI searched for Laser mast diameter and found this.
https://sailingforums.com/threads/what- ... ser.24034/So the Laser mast is 2.5" diameter. If the mast pocket on the 12 will take that mast, life just got a lot easier for you!
So, parts from Laser, Force 5, and Zuma may work for you. I've sailed Lasers, and the 12 does look similar. I owned a Hobie Hawk 9 for a while (little sister to the 12.) Fun little boat. And I mean little!
Here's some sail information from Sailrite. They sell sails, sail kits, materials, sewing machines. All the big wide stuff for a sailboat.
https://www.sailrite.com/Holder-12-Sail-DataMatt Miller is a goldmine!
https://www.hobie.com/forums/viewtopic.php?f=20&t=47702I've bought from SLO before. Good people. Here's a sail. (I'm kind of getting into this search, if you hadn't guessed. Rather than ad posts, I just edit this one.)
https://www.slosailandcanvas.com/holder ... ail-white/SCORE! Looks like Laser stuff will work. Plus these guys seem to have parts. (Man, the interwebs is fun...)
http://ms-pyc.com/midwest-sailing/parts ... ock-parts/