Neither of my dictionaries gives a perfective for this imperfective. Is there an appropriate perfective form of this verb, or should I buy better dictionaries?
The choice of one aspect over another for verbs belonging to the same root doesn't signal a grammatical change exclusively, but also a semantic one.
Many verbs (but definitely not all of them, and perhaps even not most) do have a sort of default perfective, usually formed with the prefix по-.
If you take the blandest, most simplistic, neutral phrase consisting of a subject and an imperfective predicate in the present tense, in many cases you'll be able to put it into the future tense by replacing the verb with its "default" perfective: я сплю / я посплю, я ем / я поем, я работаю / я поработаю, and most speakers will still perceive it as the same phrase, just with the tense changed.
However, in many other cases, that doesn't quite work. You can say я пишу / я попишу, я хожу / я похожу, я делаю / я поделаю, and those would be valid phrases, but fewer people would feel that it's the same phrase with just the tense changed. Я напишу / я схожу / я сделаю would be more plausible outcomes for "just put this into the future tense". These too are valid perfective verbs, but they have different meanings.
To answer your question: the verb попутешествую is a thing, and it's mentioned in Russian Wiktionary as the "corresponding perfective form" of путешествовать. But there are also many others, and the very semantics of this verb makes it hard to choose the most appropriate candidate for the "default" perfective form.
In Russian, unlike English, "travel", путешествовать is more about the process, so you wouldn't translate something like "I'm going to travel to Rome for a conference" using this verb. It's more like "to be travelling", or "be a traveler", or even "live a nomadic life", if you will. Perfective verbs require a change in state. So what is the "default" change in state for being a traveler? Start the nomadic life (запутешествую)? Have travelled enough to cross it off your bucket list (попутешествую)? Stop being fit for nomadic life (отпутешествую)? There's no uniform answer to that. That's probably why your dictionaries don't cite one single corresponding perfective.
The perfective form is попутешествовать. But this perfective form does not reflect the classical aspect ratio: prolonged action - result of action. It's this ratio that's considered exemplary and is usually cited in dictionaries. Verbs with a different ratio (and there are many such verbs) are usually cited in dictionaries without a corresponding pair.
Путешествовать belongs to a class of verbs denoting "a social state not tied to a period of time": руководить, управлять, царствовать, воровать, изучать, учительствовать, торговать, вдовствовать, питаться... In these verbs, the рerfective is most often formed with по- (=to do an action for some time); other prefixes change the semantics of the verb.
If you want to talk about a past trip, these phrases might come in handy:
- "I've travelled to Europe" - "Я побывал в Европе" or "Я съездил в Европу"
- "I travelled to Europe three times" - "Я бывал/был в Европе три раза" or "Я ездил в Европу три раза"
- "During my last trip to Europe..." - "Во время моей последней поездки в Европу..."