Track Rod Ends should be easy enough to find, mine needed one this year and there were plenty at our local motorfactors and ebay. For the arm, as mentioned MGF n TF Bitz at www.mgfntfbitz.co.uk, give them a call direct as they have most parts and don't have everything in the ebay shop.
Also MG Owners club again as mentioned. They have a shop website where you can drill down and identify the part you need, which will then give you options on price and purchase. IF available there will be a clickable link.
