I don’t think this is a good idea. I’d sooner find someone with a sewing machine who can teach you. Using a sewing machine is easy, whereas sewing thick neoprene by hand would be very difficult and time-consuming, even for an experienced person.
I actually have a full sized pattern with instructions I bought years ago to make a tuilik – it included a strip of material (sticky sided neoprene) to make the cockpit grip but I seem to have lost track of that (it may turn up over the next week as I continue to unpack and set up my sewing and project room from the move last year.
A guy named Shawn Baker got permission from H. Petersen and Wolfgang Brinck to copy their design for one. The instructions include detailed illustrations of how to join neoprene pieces by hand sewing.
QajaqUSA used to sell it in their online store but I see it no longer listed as a buy option.
https://www.qajaqusa.org/content.aspx?page_id=22&club_id=349669&module_id=358277
I am pretty sure my local Office Depot print service can scan and reproduce these 36" x 44" sized sheets. I could send you a copy if you want.
There is also a cagoule sewing pattern produced by The Rain Shed Inc. in Corvallis, Oregon (Seattle Fabrics sells these) that I had previously bought thinking it could be used with a lower body modification to create a tuilik from neoprene or a storm cag from GoreTex.
For those interested, Turner Wilson of KayakWays.net has confirmed to me that Brooks Greenland Gear is in business and taking orders. Apparently they’d been on an extended vacation in Asia.
It can be frustrating not getting a response from Brooks. While I haven’t dealt with them directly, some customers report slow replies, especially during busy times, but that doesn’t mean they’ve gone out of business. You might try contacting them via social media or calling if a number is available. Alternatively, check if third-party retailers carry their products. Recent reviews might also give you a better idea of their current service status and responsiveness.
As was mentioned back in May, Brooks was bought out a few years ago and the new owners have discontinued Greenland gear.
You might find some old gear kicking about online.
I did contact your friend again because now I have a kayak coming that does have an ocean cockpit, but I am too late. He donated it. My timing was bad
I bought a Reed tulik for my Chatham, but now I’ll be watching for a tulik made for an ocean cockpit too. I have a Rebel TOC paid for and I am supposed to get it in March.