what happens if no insurance companies want to offer a plan that does that?
The solution that Alito cited that was in place for religious non-profit and church organizations was for the insurance company to be required to pay for the drugs out of their own pockets and establish a separate pool of money for doing so, that the religious institutions would not pay into. The government considered this to be acceptable because the drugs are cheaper than pregnancy care so the insurance company would save money. The next step will be Christian Brothers Services (a religious health insurance company) suing against being forced to pay for this from their own pocket.
Once that plays out, this decision may end up having little to do with contraception or abortion. In the majority opinion, authored by Alito, he claims their decision only covers contraception, but the only citation he has to prove this is his say-so. The RFRA does not specify any limits on the ability to practice religion (indeed, that was the point of it, it originally existed so that Native Americans can ignore the Controlled Substances Act when it comes to peyote) beyond a "compelling government interest".
Alito's decision that "for-profits should be given the same religious options as non-profits" is an obvious one with respect to this particular case where the government has already given an alternate option to other companies, but it's clear from the situation leading to the passage of the law (Native Americans smoking peyote) that when there is no "alternative option", the intent of the law is to allow "the religious" to ignore laws that would prevent them from practicing their religion.
What will likely happen is one of three things:
1) Nobody pushes their luck. The elephant just sits there, in the corner of the room, and nobody ever mentions it again.
2) Someone declares ___ is preventing them from practicing their religion and sues. A court of appeals cites the text of Alito's decision that this can only apply to abortion and squashes it, SCOTUS refuses certioari.
3) Someone declares ___ is preventing them from practicing their religion and sues and ends up heard by the supreme court. Either
A) The court has to decide that Alito was wrong and the RFRA/First Amendment protects more than just your stance on abortion, and places no limit on it
B) The court cites the text of Alito's decision and denies that practice with no further explanation. Or perhaps the court decides that "interstate trade" is a "compelling government interest".
C) The court has to establish a yardstick by which the sincerity of your beliefs are measured. You skipped church for the Superbowl? Mmmhmmm, I see...