I have made shipments to the islands. Sending to St Martin is a snap through Four Star Cargo in Miami. They will ship to Grenada (and other islands) also but the broker in Grenada is on Island Time. It adds to the cost, but sometimes you get the bear and sometimes the bear gets you. Life happens.So you need a part.
In US get on IPad. Find manufacturer, various vendors, distributors. Compare costs and availability. Maybe get it on eBay, or amazon or defender or west or maybe get in care and go to distributor or directly to manufacturer.
In Windwards go to IWW or budget or small specialty shop. Maybe wait a week. Maybe another week for broker to get his act together. Or maybe three weeks so go off cruising after paying with intention of stopping back when available.
Still, in US you’ll get it and be able to shop for best price.
In Windwards if volume falls sufficiently mechanics of importation become so difficult as to make access impossible. Have had stuff fedexed to me. Have had occasion where local shops don’t carry or have in catalogue or have no interest in getting me a part unless they do the install. Unless you are a long term marina resident or real friendly with a local arranging a shipping address is difficult. So if charter business collapses and doesn’t come back or number of cruisers falls sufficiently long term cruising will below increasingly more difficult and expensive.
Used to take two passages a year. One R.I. To Caribbean. Other Caribbean to R.I. Allowed very limited marina time. Allowed restocking all spares, tools and non food supplies for the year without difficulties. Once when getting home. Again just before leaving. Passage is hard on you and the boat. Last year just stored in Caribbean for hurricane season. No passages. Easy on the boat and you. Think if things go south with the islands boating services infrastructure will be forced to do biannual passages again.
I find the costs are not too very bad. 2 years ago I made some aluminum hatch covers. I actually made them 2 sides of my shipping container to save space and shipped them on as checked baggage. The “box” was chock full of parts.
This year I ended up with 3 packages that included custom Ss handrails and a 2 piece aluminum tiller and a custom radar mount among other things. It was a bit of a hassle. Fed Ex to Miami, air freight to Grenada, broker to clear customs. It took a while but it worked. And a whole lot less than doing a round trip back to the states.
Hell 3 years ago I shipped a maple butter block counter top from the USA to Canada. That was much more complicated. I needed 2 different shippers and a customs broker and a guy to do the pick up 4 hours away.