Welcome to the Strelets Forum. Please feel free to discuss any aspect of 1/72 scale plastic figures, not simply Strelets. If you have any questions about our products then we will answer them here.
By their current available stock Sentry Box in Calgary Canada has multiple boxes of Imex Mexicans in 1/72. Don’t know what color they are but you can ask them as I’ve found them very personable and helpful. You email them your want list, include your address and contact info and PayPal and they total it up with postage and send you a PayPal request. EZ PZ. My last order took only a week, but the average is 10 days to two weeks mail travel. If you ask for tracking info they will email the Canadian customs number. Once it tracks to handoff to US customs/mail then you can try to track it thru USPS tracking with the same Canadian number. I’ve ordered from them 3-4 times now with absolutely no problem. They do not carry a lot of RedBox at all however, and I don’t see the Richelieu/Musketeer sets you are looking for.
On EBay, Dauntless Hobby in California has a couple of Red Box Richelieu figure sets. I’ve ordered from him MANY times and one of my favorite EBay sellers. His Red Box are listed at $8.99 + $4.95 each, but in his item photos the figures of foot and riders are gray. Only the horses are red. If you order multiples use this seller’s cart system as combined shipping will automatically be applied and save you money.
I second that Toby, Dauntless hobbies always has a good stock and great prices. Scott is a pleasure to deal with. Anyone looking for any sets should start there.
Judt received the parcel, Musketeers are in grey, Guards of Richelieu in red plastic. Just the men on foot, didn't order the mounted version. You should contact the seller before ordering if the color is important to you. If you're in the UK you could give Kamar a try, if in the US or Canada it's probably cheaper to try a local seller.
From Kamar Figureen, a German seller. Link is in PSR, you can contact them via their website, they've got an online shop and you can pay with paypal. They're really nice and still have some rarer sets. Note that the "command sprue" of the Richelieu set is in grey plastic (as shown by PSR) the rest is in red. PSR also has only grey as color for the Musketeers, don't know if they were ever made in red, perhaps it's a confusion with the Ultima Ratio set?