This has nothing to do with the ability to procure petroleum during “normal” circumstances, and the agreement that has not been renewed applies directly to the sceario concerning need when Israel is unable to procure petroleum when it needs it desperately.
This is a very bad development for the security of Israel, and to deny such is absurd. Such a development, if it continues, is basically a statement that the US will turn its back on Israel when Israel's existence is on the line.
Oil is typically not purchased directly from an oil producing country, but on an exchange where the source of the oil purchased is unknown and the seller has little say in who buys on the exchange.
“If the bulk of ME countries decide to boycott Israel in a time of all out war, where does Israel turn for a vital resource?”
They go to the IPE and buy oil futures like everyone else.
The structure of oil market has changed over the last 40 years and the current structure would make it extremely difficult for an oil producing country to pull off of its oil off the market or placing an embargo on Israel.