It should be possible to make a replacement wooden mast using a length of pine dowel of the same diameter as the existing mast. It is not so easy to find good materials these days but as long as it is straight, straight grained and free from knots it should be OK as a starting point. If you buy from a well known DIY supplier just be careful that it is a single piece of timber, not one that had been joined by a scarfed joint along its length. Its possible to taper the top half of the mast using a small plane and finish by wrapping a piece of abrasive paper around it to sand it smooth. Roll it along a flat surface every so often to check you are planing it down symmetrically.
Alternatively you could use a length of aluminium tube, typically 10 mm OD and 1 mm wall thickness would be OK for a 36R.
I restored a Lancet last year as a lock down project and it sails very well. However I took a short cut and borrowed a rig from another similar aged 36R that we have. If you need a copy of the original drawing I could let you have one if you pm me your email address.