If it were my cow, I’d tie her up, and even put hobbles on her back legs, and make sure the calf drinks.
I don’t have any advice regarding store bought colostrum, never had to use it myself.
I’d try to find some other farmer/homesteader that could sell me some frozen colostrum maybe?
Here is a cow forum you might wanna try and ask, there are people from all over the world https://familycow.proboards.com
I don’t think it’s against the rules to post the above link?