Working with a realtor is often a good way to locate a rental but it sounds like nothing was accomplished when using their services. As for other strategies to try:
1. There are a number of rental tools to use that helps map the area you are interested in and will show inventory on the market. Some to try include:
https://hotpads.com/ (offers "heat maps" that let you compare rental and for-sale home inventory across neighborhoods)
2. Looking into talking with an apartment broker who know the area and will specilaize in apartment rentals in Smithtown over just using a regular realitor:
3. Make an appointment to see the apartment before the Open House. Also call, don’t email. You’ll get a faster response.
4. Contact the Chamber of Commerce to see what services they can recommend. Those that want to live in this community are helped by the chamber so asking what ideas they may have would not hurt:
5. Look at the local newspaper on weekends for rental listings as the majority of rentals will be listed then.
6. Online publications on the town will often list rentals:
I hope these suggestions are found helpful as please let me know of any questions/concerns you have. Also if you could take a quick moment to rate my assistance so that I can receive credit for helping you today.