A Realtor should be able to pull that up on the MLS. There are actually two sources of information, and you want both. One is the tax records and, in fact, you probably can access those yourself online. Just Google "Suffolk County tax assessor" and that should get you pretty close. In many jurisdictions, that information is free and online. The MLS will also have historical information. You need both because: (1) not all transactions were listed on the MLS, and (2) the tax records will show the transfers, but not seller concessions or other useful information that your MLS probably has online. To get the MLS information, you'll need a real estate agent who is a member of that particular listing service.
Hope that helps.