Deere dealer says none available any more for this tractor.
Dealer is wrong and needs a better parts guy.

There are a couple different options:
RE22334 FOUR-POST ROLL-GARD W/ CANOPY [SN 024501-] (contact dealer for availability, so likely NLA)
AR95820 TWO-POST ROLL-GARD AND SEAT BELT [SN -024500] (contact dealer for availability, so likely NLA)
RE58266 FOLDABLE ROPS W/ SEAT BELT [SN -024500] (SUBS TO AR41762, R41355, R52238, RE58258, AR93828, R117491)

I would assume your SN is below 024500 since 1979 starts at 007434 which means you can still get a ROPS from Deere, but it is the foldable version.

With that said, I would encourage you to look at the National ROPS Rebate Program which covers 70% of the cost.  Since the RE58266 subs to several parts that come to $4195.14, out-of-pocket cost would be $1258.54 with National ROPS Rebate program covering the remaining $2936.60; if you are from IN, MN, NH, NY, PA, or WI the cost is capped at $500 out-of-pocket for the farmer so National ROPS Rebate Program would cover $3695.14

https://www.ropsr4u.org/

Edit to add:
Deere bulletin:
https://jdparts.deere.com/partsmkt/unsecured/document/english/pmac/5352_fb_ROPS.htm

Upon further inspection, if you want a rigid ROPS for a 4240 you would need to order
(1)  AR41762 – Hardware kit  (in AR51416)
(1)  AR51417 – ROPS (in AR51416)
(1)  AR93828 – Isolator
(2)  R41355 – Plate (in AR51416)
(2)  R42579 – Strap (early 4240 used 4 of R41355, two were used as strap/spacer)
(8)  R42581 – Bolt 

If it was me I would order AR51416, then get R47292 label to replace T27155 label in AR51416 kit, AR93828, (2) R41355, and (8) R42581 to replace R42439 in AR51416 kit for a cost of 2544.44 vs 4195.14 and end up with the same parts.

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