First of all, you can't get a shipping quote from anyone without the buyers actual address . . . read on.
I ship stuff internationally several times a week. It can be simple if you have a PayPal account. Your buyer can use his credit card to buy your skis after you create a PayPal invoice on their web site. He does not need a PayPal account to use his credit card to pay your PayPal invoice that PayPal has emailed to your buyer. You also get a significant shipping discount if you go through PayPal, but there will be a 3% fee on the price of skis for the transaction.
Then for shipping, all PayPal shipping now goes through ShipStation. PayPal with hook you up to ShipStation when you click on "Create Shipping Label". There you create a label and the Customs Declaration Form by filling in the blanks. ShipStation will provide pricing for USPS and UPS and DHL. You can choose. Their pricing will be better than walking into a UPS Store etc. and process is simply filling in the forms on the ShipStation web site.
USPS has become the least reliable because they still have staffing issues and the tracking is handed over to the UK postal service with sketchy tracking reliability in the process. I have had packages disappear at the first stop in Illinois with their international shipping, and could not find a way to make a claim. The tracking would just end at their Global transfer station and that was the end of it. I was only dealing with a $100 item and I just gave it up.
Instead of using PayPal you can just walk into a DHL or UPS retail location but you will pay more and have to deal with the customs forms across the counter.
As noted, you can't get a shipping quote from anyone if you don't have your buyer's verified shipping address.
To get shipping pricing in advance, you could get a quote at a UPS Store for shipping. You could then use the UPS quote amount with your customer and then continue to get your best price from PayPal/ShipStation. If you over-charged your customer for shipping using the UPS quote, you can agree in advance that you will refund the buyer the overage, which is simple with the PayPal transaction.
Comment . . on the ShipStation web site, the Customs Declaration asks for some kind Homoligation code categorizing the product your shipping. If a manufacturer is shipping something they would have the code to categorize it. Its similar in concept to the UPC code but its not a UPC code.
You can leave the code field blank and just provide the product description "Water Ski Pair" quantity "1" Value "$900".
You won't know the customs fees your customer will have to pay when he receives or claims the item. You should tell him that the customs fees are his responsibility paid at his end.
"disclaimer" someone else may have better information. This is my PayPal centric experience having shipped hundreds of items internationally over the last 10 years.
Another PayPal comment . . PayPal allows transferring funds between friends and family without the 3% fee. I don't think that applies if you are using their invoicing and shipping services.
If you use something like Venmo there may be no fee, but you are on your own with shipping without the simplicity of the PayPal/Shipstation service with their integrated on-line Customs Declaration.