Called Univair. After 20 minutes on the phone with them they advised they no longer sell parts for either the nose or main landing gear, including the wheels. I also checked with Parker Aerospace (Cleveland Wheels) and they advised the 40-17 is obsolete but the 40-77 is "close". The TCDS gives these options for the nose wheel:
(d) Cleveland 5.00-5, Model 21-100D (Type 40-17) Neglect wt. change
(e) Goodyear 5.00-5, P/N 9532926 Neglect wt. change
The 40-77 shows in the Parker Catalog under the 21-100D number but there are several letter suffixes after 40-77. Differences seem to be in the wheel halves and seals. I know I can rule out the versions with spacers or O-rings for tubeless tires. Does anyone have specific knowledge of the 40-77 wheels?