Good luck. I have recently found Winchester, Federal and Brenneke but haven't seen any Remington. Here is how I have been finding slugs: Go to MidwayUSA and set up an account, doesn't cost anything, and then go to the ammo you want and if it is out of stock, which it probably will be, you can click on the "notify me" tab and they will send you an email when it is in stock. One word of warning though when they send you the email you need to act quick.
As a public service announcement MidwayUSA had Winchester rifled lead slugs on stock 2 days ago for $5.99 a 5 pack.