Had flights booked (economy) LON-TLV-LON 26th-28th May which have just been cancelled (I have plans in TLV for the 27th)

Called the Gold line to ask about rebooking with El Al: they say there is no El Al availability for London to Tel Aviv between Fri 23rd and Mon 26th May. According to them my only option is to cancel (surely I can move the booking to a later date?). I said what about if I found an alternative flight, would they cover the cost, or could get reroute me eg via Cyprus or Istanbul. Agent said no to both.

Google flights shows El Al economy LON-TLV available on 27th, but nothing back from TLV-LON for the next week

Suggestions welcomed!