Your clients appear to be product makers or brand managers. You specifically work with their marketing departments I would guess?  These departments will also be working with the people in charge of marketing at their customers company’s as usually they do joint promoting as well. 

Now would be a good time to ask for referrals downstream. While a liquor company may need approval of its materials from the government a bar won’t and will still be advertising. The benefit to your core clients is that if you are making materials for both them and their clients it makes integrating items easier and a benifit for the downstream clients is that you can help them get the most from their suppliers marketing system since you know it so well.

While I’m sure you can come up with multiple benefits for both sides the key is getting your current clients to put you in touch with their customers. Don’t be put off from using your current lack of business for sympathy referrals. Normally not an ideal marketing or networking strategy but with the unique circumstances your clients are aware of strains being put on others as well as themselves. Take advantage of the “everyone in the same leaky boat” effect since it won’t stay forever.