You could try something like this that clips on to the kennel - this one doesn't look particularly secure but something with good attachments shouldn't be too flippable or spillable.
Edit - here's one that's designed just for that spill-proof purpose! http://www.amazon.com/dp/B0012GS73S/ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=1944687722&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000GDZ0GK&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0A6HMY62YFZWPN6SQE5B