Wayne: There are replacement ones out there and Aero-Lite is one source. For the cost of a couple of LED replacements, you can get boxes of NOS and new manufacture incandescent ones on fleabay. Best place to try there is "The Game Room Guys", as they have tons of parts for old pinball machines. When I looked a few minutes ago, they had boxes of #51's for 12.49$ a box and new manufacture Eiko #47's for 12.99$ a box.
Craig
KF5JOT