Bij elke Outdoor/Kampeerwinkel. Er zit een universeel ventiel op:
http://r.twenga.nl/g3.php?pg=VDsxNjY1MDgwNzI1MDg4NDUzMTg7MjA0Mjg5MTtodHRwOi8vZWNzLW5sLmtlbGtvby5ubC9jdGwvZ28vc2l0ZXNlYXJjaEdvPy50cz0xMzM3MDUyNzIzNzMwJi5zaWc9NzdObjBqTnV1SE9wWXBlcVhncHBUbTFGTlpjLSZvZmZlcklkPWUwNWQ2OTNmZWMzNmExMGVjMmQ5YjMwMGUxMjFmZWU3JnNlYXJjaElkPTEwNzY5ODIwNDExNjQzXzEzMzcwNTI3MjM3MjhfMjU4Njc0NyZhZmZpbGlhdGlvbklkPTk2OTQyMTU2JmNvdW50cnk9bmwmd2FpdD10cnVlJmVjcz1vayZjb250ZXh0TGV2ZWw9MSZtZXJjaGFudGlkPTM0NzgxMDEmY29tSWQ9MzQ3ODEwMSZjYXRJZD0xNjQ0MDE7ZDNlMWFiZjE1ZGRmNThjZjhhOWQ3Nzg0ZWJkODdhNDU=