You need the coöperation of the ISP(s), but what you can do is get PI space, run BGP on your router, and use a private ASN (64512-65534) to advertise to your ISP, and then your ISP advertises to the world with their ASN.

One common scenario is two links to the same ISP, so everyone knows which link is active (you can do active-active (load balancing/sharing), or change weights or local preference for active-passive):

* https://learn.nsrc.org/bgp/two_links_one_isp_backup

* https://learn.nsrc.org/bgp/two_links_one_isp_load_balancing