The problem with a motion detection is is - how often would the rats/mice set it off?
And they're not as direct a light but maybe one of these? https://www.robertdyas.co.uk/osram-nightlux-hall-white?___store=robertdyas_uk_main_en_gb&refSrc=95431&nosto=ab-test-brand
Decent head torch. Or a hat with a built in torch, You don't have to worry about leaving it on, you always remember to take it home to charge it. And it always lights up whatever it is you want to look at .
Personally I always liked the special edition purple/lilac colour they did. it's just a bit different. Then again our cars are red and red & silver, luckily the trailer we got is silver.
Try your local horse rescue charity. SAFE is ours, they get donated hundreds of rugs that they cannot possibly use, these are cleaned, repaired and sold to provide funds. Also good for miscellaneous tack. All very reasonably priced to clear.
I think you can train them to not poo / only poo on the move, certainly daughter's pony got booted on and gave up trying to stop. Current horse in 7 years of ownership has never ever pooed in any arena, admittedly does several bowel evacuations as soon as she thinks she is going somewhere...
Can I suggest she joins Pony Club to meet other pony riding children of a similar age and to have fun. Honestly it was the best thing my daughter did, the lessons are cheaper than riding school with some fabulous instructors (typically 1/3 to 1/2 the cost of riding school), and they do great...
Lucky here as OH is into vintage tractors and equipment, so actually enjoys using his pride and joy tractor and bailer, we also do the neighbour's in return for the hay, and sell our surplus locally for £4-5 a bale (just under current local market price), there are a couple of ladies that...
Our yard isn't too muddy so I buy steel toe capped De Walt Titanium Safety boots - about £85 from Screwfix, they're waterproof, I can wash them off under the tap while wearing them, last at least 3 years before the leather cracks through or they wear out.
We are just speculating how much it would cost for, say, 1 showing class + 1 night's stabling at HOYS (not including bedding and feed etc). I say definitely no change from £140, and probably more than that. My friend says she reckons she'd have to spend £100 or so. Neither of us have a clue...
Ask or look on local Facebook marketplace, often lots of riding gear for kids, so pretty easy to buy some jods for under £5, ditto boots usually £5-10. I'd only buy a new hat, but usually riding schools have loan ones, a new kids hat is £35-50, best you get it properly fitted