Finding a collar for that Sigma can be a pain since they dont always include one. Ive used a few third-party ones that actually hold up well for under 50 bucks.

• iShoot IS-SM105 Metal Tripod Mount Ring: Super solid and has a built-in Arca-Swiss base.
• Haoge LMR-SM105 Lens Collar for Sigma 105mm: Pretty much same quality, maybe a bit smoother finish. Either should work for your bug shoot. Just check your specific version.

Yo, late to the party but I had to jump in! Macro photography is seriously addictive once you start. I remember my first big shoot down in the Everglades... I didnt have a collar back then and my tripod head kept sagging because that lens is a bit of a beast when youre leaning in. I spent more time fighting gravity than actually focusing on the dragonflies! Since youre on a tight budget, I really recommend looking at the Kiwi Photos Tripod Mount Ring for Sigma 105mm f2.8. It is super solid for the price and leaves you with enough cash for a cheap flash diffuser or some snacks for the trail. A few quick tips for your Saturday shoot:

• Check the clearance on your tripod head so the ring knob doesnt hit the plate
• If the ring feels even slightly loose, a tiny strip of gaffer tape inside works wonders
• Look at websites like MPB or the used section on B&H for deals on these small parts Definitely check out the MacroWorld forums too if you want more tips on DIY macro setups. Those guys are wizards with budget gear! Honestly, the glass you bought is legendary, you are gonna have an amazing time with those Florida bugs! If you are worried about the Saturday deadline, maybe check if a local shop has a used Sigma TS-111 Tripod Socket since that is the official one, but it is usually pricey new. Just bring plenty of bug spray for yourself too lol. Good luck with the shoot, it is gonna be awesome!

To add to the point above: honestly, you are making the right move by getting a collar now rather than later. Ive been shooting macro for decades and trying to balance that 105mm on a standard tripod head without a collar is just asking for a headache. The weight distribution is all wrong and you will find your frame drifting down every time you let go of the camera. I have been very satisfied with the Vello Tripod Collar A for Sigma over the years. When you compare it to the official Sigma TS-21 Tripod Socket, the build quality is surprisingly close for a fraction of the price. The main thing you are looking for is a solid locking mechanism and a smooth inner surface. Some of the super cheap ones have rough edges that can scuff your lens barrel, but the Vello or even the iShoot IS-SM105 Tripod Mount Ring use a decent lining that wont ruin your gear. Just make sure you get it seated perfectly in the groove before you tighten it down... nothing worse than a lens rotating when you dont want it to. Since you are in Florida doing bugs, you will probably be at weird angles near the ground, so that 90-degree rotation a collar gives you is gonna be a lifesaver for switching to portrait mode fast.

Just saw this. Mengs IS-SM105 Aluminum Tripod Mount Ring for Sigma 105mm f2.8 DG DN Art is a solid budget choice. It holds steady enough for those Florida bugs, definitely under your 50 dollar limit.

Exactly what I was thinking