Additional OPTIONAL Upsell on Signup

Is there a way to offer additional AND optional
upsell to the visitors on the signup page?

Here's what I mean:

I have a main downloadable product, which costs
$40. On the signup page I want to offer additional
OPTIONAL purchase of "Permanent Access to The
Product" (never expiring link) for another $5.

So if visitor chooses to add that Never-Expiring
link to his purchase he'll be charged $45.

The only way I figured out it would be possible, is
to create two products (one for $40 - standard
product; and another for $45 - standard product +
$5 link) with different "negative" price groups.
And then add a check-box on the signup page with
some javascripts which automatically redirects
them to the higher-priced product, if they choose to
add that Never-Expiring link to their purchase by clicking
on the check-box.

But maybe there's a more elegant and simple way to
do it?

You can put the upsell on the thank you page, its not one click, but it works.

David