Make a kickass custom cord. Get some 10/3 SOOW cable, male NEMA 5-20 plug, female NEMA L14-30 plug. When connecting up the L14 plug, add a jumper between the two hot legs. Shop on eBay, and you can make up an excellent 30 foot cord for about $60.
As you only have an 1800 watt generator, so...