.410 Choke Tube Compatability

[Sidewinder]

I recently purchased a .410 barrel for my Thompson Center Contender G2. It has a "Full Choke" choke tube installed. I wish I could find a "Modified" choke tube for it... without having to have one made on a custom order from Briley or Hastings. My question is this... does anyone have any experience with various choke tubes in the ".410" bore? Specifically, I'm interested in what other brands might be compatible with the "Contender" barrel. Rem-Chokes are about the most reasonably priced tubes, but I'm not sure Remington made a set of choke tubes for their .410 bore. Any information is appreciated. 

[Sidewinder]

Update: Well I ordered a couple of choke tubes from Brownells, got them, and they would not fit. The threads looked about right in coarseness and they were up near the muzzle, but the tube wouldn't go into the barrel far enough to engage the threads. It started binding before the choke tube threads reached the barrel threads. If there's anyone with experience in these TC Contender .410 "shotgun barrels 21") I sure could use some words of wisdom. Thanks.