The plastic covering the cocking handle on my HK-91 broke and I would like to replace it with the HK-21 cocking handle.  I've seen it on 91's before but does this require custom work?  Also, where can I get a HK-21 cocking handle.  I saw them at Cal's Sporting Armory but they were asking $40 for them and they were out of stock.  Anywhere else cheaper?  

Also, if I decide to get another HK-91 cocking handle I'll need to know where to get one.  POF-USA has black cocking handles for $12 but I'd like to get an original HK.  

How hard is it to replace the cocking handle?

1. Pay careful attention to how the cocking lever return spring is positioned in the original cocking lever.
2. Move the cocking lever support towards the rear of the cocking tube and rotate it until the cocking lever axle pin is visible in the 2 holes at the rear of the cocking tube.
3. Punch the cocking lever axle pin through from left to right.
4. Remove the cocking lever. Don't loose the spring!
5. Install the cocking lever in reverse order of the disassembly.

To get a 21 handle to fit, it takes a bit of work.  Gordon Miller is the only guy I've seen have them pre-modified for the 91, but they are quite expensive.  If you will be happy with the factory 91 knob, RTG has them for around $12.00.  They are the new style rubber coated handles.