Vacuum pump rings may not restrict enough blood flow for effective clamping. Although, there are tons of homemade and hardware options you could try such as hose clamps with a hex driver or turn key cable clamps, a small strap pipe wrench, there’s dozens of options.
If you have hardware stores over there you could find velcro strap cable ties which would work well with some padding. Bibs uli thing isn’t a bad option if you have the tools to make it. Electrical ground covers have with two wing nuts would act as a clamp although it may be uncomfortable. Be creative and who knows, you may invent the next clamp we all love and use.