I understand that the wired remote for the LS 300 uses a LIN C protocol to communicate. The least expensive LIN C wired remote I've been able to find is the Acebil SZ300 which includes a record switch and a zoom control for $103 at B&H. (There was also a eBank controller for $22.50 on Amazon but the reviews make it sound like junk.) I don't really need the zoom switch, just a record button. Has anyone seen a LIN C wired remote with a record button that's cheaper than $103?

I'm using the VariZoom VZRock with my LS-300. A bit more expensive, but I find the extra features very useful. The zoom rocker works beautifully with the VSM zoom feature, and I find the focus button valuable when I have an autofocus lens mounted.

I was going to recommend the VZ Rock as well. Disclaimer: I used to work for VariZoom back in the late '90's. Despite the fact that I'm no longer with the company, somehow they still manage make excellent equipment. How can they do that without me? But they do. Costs a bit more but well worth it.

The control protocol is LANC and any Sony or Canon controller should work with the LS300. Try this:

VariZoom VZRock for LANC Camcorders (https://www.bhphotovideo.com/c/product/330007-REG/VariZoom_VZ_ROCK_VZRock_Variable_Rocker_for_LANC.html/BI=2855&KBID=3801) at B&H

I have a Sony LANC VZ Rock that I use on my JVC cameras and it works 90%. One button doesn't communicate with the JVC cameras (don't remember which) but all the really important ones (zoom, focus, record) do work.

The REC remote I use on my LS300 is called the JJC HR Pistol Grip, for Sony/BM cameras, works fine on LS300. It's $25 on 'bay or 'zon. I purchased the LANC model for BM cameras. Works fine on LS300.

https://www.amazon.com/JJC-HR-DV-Stabilizer-Camcorder-Blackmagic/dp/B00MRNP2LA/dvinfo09-20 (https://www.amazon.com/JJC-HR-DV-Stabilizer-Camcorder-Blackmagic/dp/B00MRNP2LA/dvinfo09-20/dvinfo09-20/dvinfo09-20)

I use it with a shoulder rig. The pistol grip shape is nice, but it's not a heavy duty design, it's semi-flimsy. It also has a ridiculous "LOCK" button that you can easily click with your hand grip on accident. If the button is clicked, it disables the REC trigger. The first thing I did was take the handle apart, remove the "LOCK" button, then put a piece of tape over the hole. Now I won't accidentally disable the REC trigger.

I have this little cheapo from back in my sony cams days

ASHANKS Zoom Control DSLR Pro Camcorder Remote Controller 2.5mm Jack Cable (https://www.amazon.com/ASHANKS-Control-Camcorder-Controller-Panasonic/dp/B00WG9IA9Q/dvinfo09-20) It works really well for zoom and rec on & off. Nothing special but reliable and gets the job done.

I picked up a Vivatar LANC from amazon for about $24 and it seems to work fairly well. Well the zoom does not seem velocity sensitve like a $200-$300 Varizoom PGL is. but set it to slowest speed and creep in and out as well as rec/pause.. hard to beat for $25. cheaply made.. won't last long.. but will get you by till you get around to buying a Varizoom which are of course great.