Search CPF for user "koala" and his M3 LED tower. There is an interest thread going on resurrecting a new round of sales.
Besides nailbender, Lumens Factory has D36 LED drop-ins. Search the Lighthound web site. However, you may have to partially disassemble your existing bezel to use these drop-ins.
Besides the Lumens Factory Seraph P7 head, goinggear.com has an MC-E head, and OpticsHQ has their TLS TX3 head.
On the homemade front, you can get a KT4 TurboHead and build an LED tower using a Netkidz tower kit (search CPF for Netkidz tower) or an AW tower kit (search the Marketplace, Dealer's Corner for AW tower sink). Add an XP-G, Seoul P4, or MC-E, and a driver and assemble.