Are you aware Remington is no longer in production? Often eBay is the sole source for replacement parts. A local Husqvarna or Stihl dealer may have a suitable substitute. Take your cover, they are most helpful weekdays before 1500.

You do not give us the model number of your saw to verify this will fit.
Remington.com
http://shoppingcart.msservicecompany.com/Default.aspx
• Type "YourModelNumber" into the "Search for your unit by Model:" window, then click search.
• Click the "YourModelNumber" - Remington Electric Chain Saw "View Model" link.
• Click "View Owners Manual" or "View Illustrated Parts Diagram" link.
• Type "YourPartNumber" into the "Search for your parts by Part #:" window, then click search.

A tension repair kit is available here:
MasterParts.com
http://www.masterparts.net/Merchant2/merchant.mvc?Screen=PROD&Store_Code=MPD&Product_Code=108640-MD
Part number 108640-MD; DESA SPECIALTY PARTS: KIT, ADJUSTMENT SCREW FOR SPROCKET COVER (REM-18); $5.95.
Kit fits the following covers: 108640-01, 116675-01 and 108641-02 (note: for the 108641-02 the screw will adjust from the front with a screw driver, not with a thumb screw at the back) KIT INCLUDES: screw, clip & adjustment block. If not available here pleasse reply (below) with that information. TIA

If you have more questions or need additional help please reply below and I will get back to you. Good Luck. HTH
Lou