contract with an SLA
Plenty of hosters provide that. Cerebras, for example, fabs their own ASICs (seperate from Nvidia), builds them into servers, hosts a number of open-weights models themselves in friendly jurisdictions, and offers SLAs for enterprise clients; it doesn't get more "guaranteed" than that in AI Land, but there are tons of hosts to choose from.
https://www.cerebras.ai/build-with-us
The major sticking point is that the best open weights models are Chinese. This doesn't actually matter from a security standpoint anymore than buying a Chinese tire does; they're dumb weights anyone can finetune, host and run on whatever software/hardware stack one wants... But try explaining that technical distinction of "using Chinese AI" to executives responsible for entire corporations.
There are even attempts to "launder" Chinese models to make them palatable for western enterprise use. For example: