What type of tenancy agreement should i use for a 3 and a half month fixed term?

i have a property that i am going to let out for 3 and half months and i'm wondering which agreement i should use. the property must be vacated by a specific day. I thought about an AST but believe the tenant can stay for a minimum of 6 months before notice of repossession can be given. Been looking for an agreement along the lines of something similar to a holiday let?

any advice would be most appreciated!