You could call around local jewelry shops and see if they have a qualified tech who could simply regulate the watch for you. "Regulate" = "adjust to make run faster/slower". This type of service would probably not come with any guarantees.
Consider that the watch slowing down indicates some other problem, like dried up lubes and/or mechanical wear. How old is the watch? This is a different question from when the watch was purchased new. Sometimes a watch sits in a store's stock for a year or more before being sold. A lot of watch manufacturers recommend 5 - 7 year service interval. Problems usually start with dried up lubes, and that leads to wear on load-bearing surfaces. This is akin to running your car's engine without oil in it, but death comes more slowly in a watch.
Do you wear the watch daily? Do you enjoy using it? Is for real water-resistance important to you? If so then consider treating it and yourself to a solid service instead of a bandage. If you only wear it occasionally and it sits in a drawer for most of its life then go for the bandage (regulation only). This is what I would tell any owner of a potential project.
Only $190 for a full service? Sounds like a deal for what you get in return, especially considering that we're talking about a factory service center and results backed up by a warranty. As an independent watchmaker I would charge you more for the same deal. It would require most of a day's labor and the use of facilities and other materials that are expensive to maintain and purchase. Here's a general run-down on what would be done:
- Watch movement removed from casing;
- Casing cleaned/polished, assembled with all new gaskets, maybe even a brand new crown and crystal;
- Movement completely disassembled, all parts cleaned, re-assembled with fresh lubrication, probably brand new mainspring and other parts as needed;
- Watch tested for performance.
Hamilton is part of the Swatch Group. Looks like you could send it in directly, or find a local dealer/rep. Check out their service page:
https://www.hamiltonwatch.com/en-int/customer-service.html
Who am I? A Swiss-trained and certified watchmaker with 25 years experience. I used to service Rolex but nowadays I only work on vintage wrist and pocket watches. My certifications are from Switzerland (WOSTEP), and the USA (AWCI's CW21).
