Just what the hell is in haggis anyway? well...
The following is the recipe for haggis that won the first prize spot at the Great Competition of Haggises in Edinburgh at the beginning of the 19th century.
You need a sheep's pluck (this includes heart, lights, and liver) and paunch, onions,oatmeal,beef suet, pepper, salt, cayenne, vinegar or lemon
"Clean a sheep's pluck thoroughly, make incisions in the heart and liver to allow the blood to flow out and par-boil the whole , letting the windpipe lie over the side of the pot to permit the discharge of impurities; the water may be changed after a few minutes boiling. A half hours boiling will be sufficient; but throw back the half of the liver to boil till it will grate easily; take the heart, the half of the liver, and part of the lights trimming away all skins and black looking parts, and mince them together. Mince also a pound of good beef suet and four or more onions. Grate the other half of the liver. Have a dozen of small onions peeled and scalded in two waters to mix with this mince. Have ready some finely ground oatmeal, toasted slowly before the fire for hours till it is light brown colour and perfectly dry. Less than two teacupsful of meal will do for this quantity of meat. Spread the mince on a board a strew the meal lightly over it, with a high seasoning of pepper, salt, and a little cayenne, first mixed well. Have a haggis bag (ie: sheep's paunch) perfectly clean, and see that there be no thin part in it, else your whole labour will be lost by it's bursting.
Some cooks use two bags, one as an outer case. Put in the meat with a half pint of good beef gravy or as much strong broth as will make it a very thick stew. Be careful not to fill the bag to full, but allow the meat room to swell; add the juice of a lemon or a little good vinegar; press out the air and sew up the bag, prick it with a large needle when it first swells in the pot to prevent bursting; let it boil slowly for three hours if large"
One might find the cayenne an odd addition. However when I was in Scotland about 5 years ago the haggis I had was surprisingly spicy, go figure. Also, if some of the ingredients don't sound like something your local grocer would have, i suggest trying a local meat store that specializes in meats of various animals and the various cuts thereof.