Well, be careful with your little dudes trachea. Small dogs have a much higher risk of trachea collapse with anything thin around their necks. And slip leads tend to be thin.

I got my little dude a martingale meant for Italian greyhounds, in a 1.5” in thickness, as not to have pressure too much in one spot on the throat. And I use a leash intended for cats and small dogs, nylon 6ft long & 3/8” thickness so super lightweight, that I bought on Amazon. https://www.amazon.com/dp/B000OGRDK0?ref_=cm_sw_r_ud_dp_6YM5JY5N6A9Y3RQHR6T2 PetSafe Nylon Dog Leash - Strong, Durable, Traditional Style Leash with Easy to Use Bolt Snap - Available in Multiple Widths and Colors

I got the nylon martingale collar at Caninuscollars.com, https://www.caninuscollars.com/colored-nylon They offer smaller and larger thicknesses (3/4” all the way up to 2” thickness) and they custom make every order. After you place the order for what you want, they’ll email you for more details (exact neck measurement and age) before they produce your item. I even sent them a pic of my big little dude.

Mine is a 20lb mixed breed and this is the combination that works the best for us for training and walking purposes after searching, buying and missing the mark a bunch for what I was looking for. Good luck! ♥️🐾