Just make a neck rest - really not that hard. I've attached several photos of Sun Tad trikes with neckrests made from automotive headrests and plastic or aluminum tube (recommended!). Two sections of aluminum tube with an ID just a little larger than the OD of the rods attached to the automotive headrest. Flatten one end of each aluminum tube and drill a hole just a little larger than the OD of the bolt used to secure the seatback adjusting tubes. Seatback and headrest tubes holes lined up and bolted to the same eyelet that the seatback tube used. Secure headrest rods to upper frame of seat using zip ties. You can make the headrest adjustable if you drill holes in the lower aluminum tube you made and use a short quick release (1"). I didn't use an automotive headrest on my trike, I used two pieces of copper tube and two copper 'els' and another short copper tube as wide as I figured the back of my neck/melon was. Wound foam around as a pad. Works well, but I do not have pictures.

Tailwinds and long downhills,

Tourezrick
'98 TE EX
'06 Ooglemobile (was Sun Tad)