I also have ILC-1, which is more expensive version, but it's drop-in module and easy to install,it fits Convoy lights,I'm don't know if it fits S41.
By default there is only one color to choose, but if you want two different colors that is possible since ILC-1 has two separated channels with constant current drive.
I think what people who are suggesting links are not understanding is that we want to buy a fully assembled one, ready to go - nothing to do to it.
Thank you for your help though.
I guess it could be made to fit as it is close. Diameter is the problem, I think it would fit nicely otherwise. However, myself, I’m not willing to file down the switch nor open up the threads in the tail.
I will soon offer ILC-1 kit without brass ring at significantly lower price than assembled ILC-1, top and bottom pcbs have 16.5mm diameter , so such "ringless" ILC-1 should fit in more lights (brass ring is not really necessary, but without it switch and top pcb should be glued to prevent twisting).