As has been stated above, if the husband gets himself added as an additional driver on any other person's policy (where he is actually the main driver of the vehicle himself) both he and the other person will be guilty of 'fraud by false representation' under Section 2 of the Fraud Act 2006, which could result in them
both being sent to prison.
All he can do is to keep seeking quotes from specialist firms. MCE Insurance is a broker that claims to specialise in helping people with motoring convictions, so it might be worth giving them a try:
http://www.mceinsurance.com/content/other-insurance/convicted-car/
Otherwise he'll have to consider:
(a) moving closer to where he works ; or
(b) arranging lifts with someone who works the same shifts as him ; or
(c) cycling to work ; or
(d) changing his job.