In context, this was a special directive from Rabbi Yehuda haNasi to his sons. It is unclear whether he actually said this, since his actual words were the cryptic "Do not sit on the bed of an Aramean woman", and this is one of several interpretations proffered by the anonymous narrative voice of the Talmud.
In context, it seems to be a matter of good advice, rather than a prohibition. (Similarly, if it means not to literally sit, based on the incident with Rav Pappa where someone tried to frame him, it is good advice. Perhaps for the meaning of not sleeping without reciting Shema, a new recital of Shema at bedtime, as opposed to e.g. saying a pasuk, is a good idea.) He is not telling them not to eat a ham sandwich, for that is not something that needs to be said to one's children as particular advice.
As such, we would not necessarily expect that such advice finds basis elsewhere in the Talmud. Rashbam in his commentary on the page, writes:
לא תינסוב גיורתא - משום דאמרינן גיורא עד עשרה דרי לא תבזי ארמאה באפיה (סנהדרין צד.):
That is, he refers us to Sanhedrin 94a, that a convert, even descendants ten generations afterwards, one should not disparage a non-Jew in front of him, because he still identifies in some small measure with than non-Jewish identity. This, firstly, might be the parallel Talmudic statement for which you are searching. But, secondly, this reinforces the idea that this is not a legal statement, but a piece of advice, on the basis of how the person's identity could impact the relationship.
However, one should note that the royal members of Rabbi Yehuda the Prince's house had their pick of spouses, and could afford to be picky in this aspect. People are complex beings, and one should consider the whole person. While this is one aspect to consider (in terms of the person themselves and the identity of descendants, assuming that Rabbi Yehuda HaNasi actually did say it to his children), there are other positive and negative traits that potential spouses have to offer, and one should not blindly refuse to marry a convert, who may be a wonderful person with whom one could built a fine Jewish household, based one line in the Talmud.