I like the Book of Bruce and am glad your brought that to everyone's attention. I did not see any primary sources in that book. I checked several publications, Burke, Paul, etc. but found nothing. I'll keep my eyes open though.
In the mean time, I formatted the citations a bit and marked the profile 'unsourced.' I noticed a reference to Burke's Peerage but no page number. The 107th edition has no online images available but the 77th and 102nd (amongst others) are available . . . unfortunately, I did not see Lucas Bruce as mentioned in the profile. Maybe someone can check the 107th edition.