Do the narrow rubber boots fit somehow onto the plugs? If they are a tight fit but go on far enough for the clip to snap with the plug then you can use them - the tight fit can actually help by sealing against the plug's ceramic.
I've rolled my own leads a couple of times and apart from using the wrong crimping tool i've never had any problems. Having a little bit of electrically insulating grease on the rubber helps getting the boots on sometimes.
Oh, and it would be best if you try the fit on a spare plug you might have lying around before you fit them on the car. I can't gaurantee anything but I've had luck in the past.
some time ago i bought some ht ledas from halfords. Can't remember the brand name, but i was also able to buy some small rubber boots from the same manufacturer that fit over the end of the lead and block up the rest of the spark plug hole. they were listed in the halfords catalogue as a fitting kit for alfa 33s...
pains me to say it, but might be worth a look round your local halfords...
With my old 33 16valve I changed the leads for some silicon ones that had a smaller diameter rubber boot than the originals. This actually made it easier to take them on and off the plugs and never gave any trouble in wet weather.
Give em a try and if you get problems just put the boots off the old leads on the new leads. Easy job to do.