You could try Bob Carnie at Elevator, in Toronto. He still does a lot of work optically, I do not know if this is something he does, but give him try. He is an APUG member, so by doing a search you should find him easily.
Keith
Im not sure where you are based but I own and operate a traditional colour and black and white darkroom in Bondi N.S.W Australia the largest size I can print to using analog printing processes is 24x36 inches.
If you would like any information on my print processes you can email me
at Steve@thelighthousebps.com.au or phone me on +61(02) 9365 6063
Steve Frizza
The Lighthouse Lab
Shop 2-219 Bondi road
Bondi N.S.W
Australia