I was able to find online some metal knobs that MIGHT work, but the prices ranged from $30 to 60 EACH, and I needed 5 - too costly for me!
The following 3 plastic knobs will work on your Jenn Air range, model JGR8875QDS. By "work" I mean they will fit your burner controls, operate the burners just like the factory knobs, and the markings on the knobs for "Off" "Lite" and "Hi" will be in the correct positions, similar to the factory knobs. (Exception: The last knob listed has markings somewhat different than the Jenn Air knobs.)
The following knobs do NOT look like your factory knobs - all three are made from black plastic rather than the (fake) silver metal look of the (plastic) OEM knobs. What I cannot tell you is if the following knobs will be more durable than the factory knobs - but then it's hard to imagine how they could be much worse.
-------- Burner control knobs known to work on the Jenn Air JGR8875QDS gas range --------
1. Whirlpool part number 74008850, made for some Amana gas ranges, will fit the Jenn Air. RepairClinic.com calls it part #1035119, and PartsSelect.com calls Item #PS2086316; it sells for $6-7 (USD). You can see a photo by entering the appropriate part number in the search box of either of the two websites mentioned above. The Amana knob is about a quarter-inch larger in diameter than the OEM knobs, but that does not cause any problems. Of the several knobs I tried this is the only one that tells me what it's made from - "PBT" - or polybutylene terephtalate, a thermoplastic which has a melting point of 430 degrees F and a maximum utilization temperature of 330 F.
2. Whirlpool part number 74009094, made for some Maytag gas ranges will also fit the Jenn Air. RepairClinic.com calls it #1035342, and PartsSelect.com calls it #PS2086544. It sells for about $9 on both sites. You can see it here:
Like the Amana knob, the Maytag knob is about a quarter-inch larger than the OEM Jenn Air knob.
3. A third knob worth considering is available from AmericanStoveParts.com for $7 each. The front of the knob looks much like their OEM Replica Burner Knob 1104-B (but don't order #1104-B - it won't fit). The knob that will fit the Jenn Air is AmericanStoveParts #1214-025-B. You will have to order it by phone or email because it is not shown on their website. (As of October 2009, none of the knobs shown on AmericanStoveParts.com will fit the Jenn Air.)
Notice the markings on the 1214-025-B are not quite like the Jenn Air markings, with the "HI" and the "LITE" positions being reversed. Also, the 1214-025-B knob I received did not have the white dot at the "OFF" position nor the white ring around the periphery as shown in the photo of the 1104B knob. The total diameter of the the 1214-025-B is 2" - the same as the factory Jenn Air knobs.
While I don't think the front of 1214-025-B looks quite as nice as the Amana or Maytag knobs, the back of the knob appears to be much more robust than on the others. The extra plastic MAY make this one more durable.
I have installed the Amana knobs (#1), and I will report back if it proves unsatisfactory.
on Jul 08, 2019