You can also get in touch with your local nappy scheme, if there is one in your area. I know that where I live, the only way to get into antenatal groups/nct/midwives, HV.... is through the nappy scheme, as they don't really like the commercial part of being an agent, but it really depends on the area.
You can maybe organise a nappuccino in a cafe/softplay well known for being child friendly, most of the time, the owner will just see it as an opportunity to bring more customers in and won't ask you to pay anything.
Have you thought about pramshops, toys shops...? they may let you put a poster/leaflets.
Hope this helps and good luck.
For Litte Lamb, there is a link at the bottom of the page about being an agent/wholesale