this might be a cheap option. nice guy from the sig forums has been working on it.
m1bullpup.com
hope it is okay to post this, lol. i am not affiliated or anything.
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REM ACOG - M1Bullpup
ACOG illuminator. It illuminates reticle of the Trijicon ACOG TA31 / M150 sight in low light conditions and reduces the reticle bloom in bright daylight.
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hope it is okay to post this, lol. i am not affiliated or anything.