Definitely ask your employer about anti fatigue mats if your required to spend significant time in one spot. Also good quality shoes are essential. I don’t like spending a lot of money on clothes and shoes for myself. But I’m a nurse and know the value of a good pair of shoes and see it as an investment. I would also recommend a visit to a podiatrist to be assessed properly for any foot issues and see if an orthotic or arch support is appropriate.
If you also suffer from aching legs, try compression socks. They look really daggy but they are effective. If you don’t ware long pants to hide them under just wear them at home in the evenings. I often wear them to bed to stop my legs aching and they help with leg cramps.

Can you not do an aldi and get a stool for quite le times?

Good insoles and quality shoes will go a long way.

If you are behind a counter I'd request an anti fatigue floor mat trip make that part of the floor softer. Otherwise as others have said, get good quality shoes and threaten with ohs obligations if you have to.

I would also be questioning why you can't wear neat sneakers.
Remind your employer of their obligations regarding OHS. Any pain/ injury relating to this and insufficient footwear is workers comp and I'm sure they don't want that.

I used to use the diabetic insoles when I was nursing. The floors were all concrete or linoleum and I have stuffed ankles from a childhood injury and the insoles made so much difference. I would also recommend what others have said and invest in some good quality supportive shoes. If I was to go back to nursing that would definitely be what if do now

Wear good quality shoes

Invest in hush puppy shoes

Arch supports have made a huge difference for me. Slip them into any shoes to give your feet the extra support they need to work so hard all day. Look up Plantar Fasciitis - and then do whatever you need to not get it! 😆😭

Insoles, all day socks - anything that puts cushioning between you & the floor. Also if you're desperate check out the where the older ladies shop for shoes, orthopedic shoes - they may not look pretty but you'll be alot happier at the end of the day.

I'd be complaining that you're not allowed to wear proper footing. Surely that's a work safe thing? I stand at a bench on a concrete floor for 8 hours every day (florist) but I'm allowed to wear correct shoes with proper support

get insoles

Mine was always being able to take my shoes off when I can, at break time, behind the counter when there weren't any customers. Stretching and massage them when I could. But I know the pain, all day on your feet, and the pain doesn't subside until very late in the night, and just to do it all over again!