You can purchase the MTH signal heads for the 11030 signal bridge, separately and avoid the hassle and labor of trying to disassemble a head to change out LEDS/
It's MTH part # 30-11030a.
If you're patient, I have seen 2 packs sell on ebay for between $15 and $20.00, or you can try contacting some of the larger dealers/OGR sponsors to see if they have them in stock.