How to prevent or block other DHCP servers?

You switches allow you to filter IP ports. So you just have to block port UDP 67 (DHCP DISCOVER) or UDP 68 (DHCP OFFER) (depend if you want to block input or output, or maybe both) except on the desired switch port.

Many manufactures of switches offer options on their managed equipment to handle this. Cisco, for example, has "DHCP snooping" that will determine where DHCP messages can come from and "IP Source Guard" that will also prevent traffic from using an IP they didn't obtain from the DHCP server. See http://www.ciscopress.com/articles/article.asp?p=1181682&seqNum=7

HP also does DHCP snooping: http://h40060.www4.hp.com/procurve/uk/en/pdfs/application-notes/AN-S12_ProCurve-DHCP-snooping-final.pdf

... and the remaining vendors of interest will be an exercise for the reader.